The three biggest contributors to the S&P 500 rise in index points since 2009 are Apple, Google and Microsoft (not far behind them is Amazon, in ninth place). Giant tech stocks have been a major part of the US market recovery. These companies are truly global, and as a result are having a significant effect on economies like Australia's: disrupting established industries, and often paying very little in tax. This invariably feeds through back to both stockmarkets. At the moment though, there is huge global appetite among investors for exposure to tech, which can't really be found in Australia.
It's a shame then, that no such businesses exist in Australia, where the market is still dominated largely by banks and miners.